In recent months, digital television has been gaining popularity with U.S. viewers. More and more local broadcasters are switching to digital transmission of television signals. In 2003, it is believed that almost all U.S. local broadcasters will be broadcasting at least part of their programming in a digital format. By 2006, many expect that digital television will be the exclusive mode of delivering live and rerun television programming in the United States.
While digital television broadcasting is a necessity for delivering high definition television (HDTV), the converse is not the case. In fact, there may be some advantages to not providing HDTV broadcasts at all times. For example, if a digital television station is not broadcasting in HDTV mode, then it is not using up its allotted spectral bandwidth. The extra bandwidth can then take the form of several digital side bands or side channels. These side channels can be used to broadcast any type of programming. Data programming, in the form of non-video textual information, consumes very little bandwidth. A typical local broadcaster's spectral allotment can simultaneously support scores of mere data channels or at least several non-HDTV television video broadcasts.
While it has been widely accepted that these side channels will exist, their optimal use has not been well understood. The most salient problem is that if the station is broadcasting some of its programming in HDTV mode, it may not be able to simultaneously and continuously provide a digital non-HDTV video side channel. Additionally, the amount of bandwidth used by a digital HDTV broadcast is not constant over time. These factors create serious limitations of the utility of this unused bandwidth.
Consequently, there exists a need for improved methods and systems for utilizing digital side channels.